/**
 * Copyright 2011 The Apache Software Foundation
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.hbase.filter;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Random;

import org.apache.hadoop.hbase.KeyValue;

/**
 * A filter that includes rows based on a chance.
 * 
 */
public class RandomRowFilter extends FilterBase {
	protected static final Random random = new Random();

	protected float chance;
	protected boolean filterOutRow;

	/**
	 * Writable constructor, do not use.
	 */
	public RandomRowFilter() {
	}

	/**
	 * Create a new filter with a specified chance for a row to be included.
	 * 
	 * @param chance
	 */
	public RandomRowFilter(float chance) {
		this.chance = chance;
	}

	/**
	 * @return The chance that a row gets included.
	 */
	public float getChance() {
		return chance;
	}

	/**
	 * Set the chance that a row is included.
	 * 
	 * @param chance
	 */
	public void setChance(float chance) {
		this.chance = chance;
	}

	@Override
	public boolean filterAllRemaining() {
		return false;
	}

	@Override
	public ReturnCode filterKeyValue(KeyValue v) {
		if (filterOutRow) {
			return ReturnCode.NEXT_ROW;
		}
		return ReturnCode.INCLUDE;
	}

	@Override
	public boolean filterRow() {
		return filterOutRow;
	}

	@Override
	public boolean filterRowKey(byte[] buffer, int offset, int length) {
		if (chance < 0) {
			// with a zero chance, the rows is always excluded
			filterOutRow = true;
		} else if (chance > 1) {
			// always included
			filterOutRow = false;
		} else {
			// roll the dice
			filterOutRow = !(random.nextFloat() < chance);
		}
		return filterOutRow;
	}

	@Override
	public void reset() {
		filterOutRow = false;
	}

	@Override
	public void readFields(DataInput in) throws IOException {
		chance = in.readFloat();
	}

	@Override
	public void write(DataOutput out) throws IOException {
		out.writeFloat(chance);
	}
}